Atec Agilent-87405A - Manual (Page 2)

2
Improve noise figure measurements
Add a preamplifier to noise figure measurement
systems to significantly lower system noise figure.
The noise figure of the system is dominated by the
noise figure of the preamplifier.
F
new
= F pa + F
sys
- 1
G
pa
Where F and G are noise figure and preamplifier
gain, both in linear terms.
NF
sys
= 10 log (F
sys
) in dB
For systems having a single preamplifier, where
the gain of the preamplifier is greater than or
equal to the spectrum analyzer noise figure, the
system noise figure approximately equals the noise
figure of the preamplifier.
Increase sensitivity and speed
Adding preamplifiers to measurement systems can
improve sensitivity for measuring low-level signals.
Boost the sensitivity of your Agilent spectrum ana-
lyzer 15 to 25 dB by using the 87405A preamplifier.
Alternatively, better sensitivity can be traded for
measurement speed. Spurious tests often require
narrow resolution bandwidths to reduce the noise
floor of the analyzer, allowing low-level signal
detection. An analyzer with low noise figure allows
you to use a wider resolution bandwidth, yet
achieve the same sensitivity. Sweeptimes can
improve one hundred fold for each decade increase
in bandwidth. The 87405A preamplifier has gain
and noise figure characteristics that optimize
dynamic range and sensitivity.
Gain (dB)
28
27
26
25
24
23
22
21
0.01 0.5 1 1.5 2 2.5 3
Frequency (GHz)
Noise Figure (dB)
10
9
8
7
6
5
4
3
0.01 0.5 1 1.5 2 2.5 3
Frequency (GHz)
2
1
Output Power (dBm) @ 1 dB compression (dB)
12
11
10
9
8
7
6
5
0.01 0.5 1 1.5 2 2.5 3
Frequency (GHz)
4
3